A press brake type bending machine, for example, is available as a conventional bending machine which is an example of a sheet metal machine.
Bending machines of this type are designed so that one of an upper table having a punch mounted thereon and a lower table having a die mounted thereon is moved upward and downward to apply bending processing to a workpiece by the cooperation of the punch and the die.
In light of this, if the bending machines are classified by a movable table (ram), they can be classified into two large groups of a lifting-up type in which the lower table is moved upward and downward and a lifting-down type in which the upper table is moved upward and downward. According to a lifting-up or lifting-down type bending machine, a back gauge device is arranged on its back part, and a workpiece is positioned prior to the bending processing, as is well known in the art.
The manual back gauge device illustrated in FIG. 9(A) and the automatic back gauge device depicted in FIG. 9(B) are available as back gauge devices for conventional lifting-up type bending machines. Either back gauge device comprises two supporters 104 extending from a lower table 100 (FIG. 9(C)) in a Y-axial direction, and posts 107 provided one on each of the supporters 104.
Of the above-described back gauge devices, the manual back gauge device (FIG. 9(A)) is one in which abutments 105 are attached to a stretch 106 engaged with screws 108 arranged at both ends of the stretch 106, and is designed so that the abutments 105 are moved in a Z-axial direction by manually rotating the screws 108.
Further, the automatic back gauge device (FIG. 9(B)) is one in which the abutments 105 attached to the stretch 106 are engaged with ball screws 110 in housings 116, and the back gauge device is designed so that the abutments 105 are moved in the Z-axial direction along guides 109 by driving motors M to rotate the ball screws 110.
However, according to the conventional lifting-up type bending machine, as should be apparent from FIG. 9(C), a stay 102 which couples side plates 103 arranged on both sides of the lower table 100, and the pressure-oil tank 111 of a cylinder 101 for the lower table 100, are provided under the supporters 104.
Consequently, because structures such as the aforementioned stay 102, etc. constitute an obstacle, the posts 107 (FIG. 9(A), FIG. 9(B)) which support the stretch 106, the screws 108 (FIG. 9(A)) included in mechanisms for driving the abutments 105, the motors M and the ball screws 110 (FIG. 9(B)) cannot be extended downward and cannot help but protrude above the abutments 105.
Because of this, when the abutments 105 are moved downward in order to apply overhang processing to a workpiece W, the workpiece W interferes with the motors M above the abutments 105 as shown in FIGS. 9(A) and 9(B), due to which the positioning of the workpiece W cannot be performed.
Meanwhile, the back gauge device illustrated in FIG. 10 is available as one for a lifting-down type bending machine.
This back gauge device includes columnar posts 107 which extend straight from the lower surfaces of both end portions of the stretch 106 to which the abutments 105 have been attached, and the columnar posts 107 have racks 107A formed thereon.
As shown in the right-hand drawing of FIG. 10, pinions 112 engaged with the aforementioned racks 107A are coupled to each other via a torsion bar 115, and the torsion bar 115 is connected to a worm gear 113 via a left-end pinion 114.
Therefore, if a motor (not shown) connected to the worm gear 113 is driven, the posts 107 move in the Z-axial direction via the pinion 114 and the pinions 112, and accordingly the abutments 105 also move in the Z-axial direction.
As explained above, according to the lifting-down type bending machine illustrated in FIG. 10, the posts 107 extend below the abutments 105. Thus, since there are no protrusions above the abutments 105, the overhang processing can be applied to the workpiece W as shown in FIGS. 9(A) and 9(B).
However, as clearly seen from FIG. 10, the space under the stretch 106 is extremely narrow, since the posts 107, the pinions 112, 114 and the worm gear 113 are arranged under the stretch 106.
Moreover, since the stretch 106 is merely supported by the two columnar posts 107, the posts 107 are liable to warp, and the stretch 106 is considerably unsteady.
On the other hand, the above-described back gauge devices can be classified into two large groups of an independent type and a non-independent type if they are classified by left- and right-hand Z-axial driving mechanisms for upwardly and downwardly moving the stretch to which the abutments have been attached.
According to an independent type back gauge device, each of the Z-axial driving mechanisms comprises a motor Mz (FIG. 11), and those mechanisms operate independently from each other when their respective motors are driven. According to a non-independent type back gauge device, the Z-axial driving mechanisms comprise a single common motor, and operate in cooperation with each other when the common motor is driven (FIG. 12).
Of the above-described back gauge devices, one including independent type Z-axial driving mechanisms has the structure shown in FIG. 11, for example, and comprises two supporters 204 extending from a lower table 200 in the Y-axial direction, posts 207 provided one on each of the supporters 204 and each having a Z-axial motor Mz, a stretch 206 extending between the two posts 207 in an X-axial direction, and abutments 205 attached onto the stretch 206.
The Z-axial motors Mz, the post 207, ball screws (not shown) incorporated in the respective posts 207 and engaged with the stretch 206, etc. form the Z-axial driving mechanisms for the stretch 206.
According to the above-described structure, when the Z-axial motors Mz provided one on each of the posts 207 are driven, both Z-axial driving mechanisms operate independently from each other to move the stretch 206 upward and downward.
Meanwhile, the back gauge device illustrated in FIG. 12, for example, is available as one including non-independent type Z-axial driving mechanisms.
This back gauge device has columnar posts 207 which extend straight from the lower surfaces of both end portions of the stretch 206 to which the abutments 205 have been attached, and the columnar posts 207 have racks 207A formed thereon.
As shown in the right-hand drawing of FIG. 12, pinions 212 engaged with the aforementioned racks 207A are coupled to each other via a torsion bar 215, the torsion bar 215 being coupled to a worm gear 213 via a left-end pinion 214, and the worm gear 213 being connected to a single common motor (not shown).
The common motor, the worm gear 213, the pinion 214, the torsion bar 215, the pinions 212, the racks 207A and the posts 207 form the Z-axial driving mechanisms for the stretch 206.
Hence, when the common motor (not shown) connected to the worm gear 213 is driven, the posts 207 move in the Z-axial direction via the pinion 214 and the pinions 212; that is, both Z-axial driving mechanisms operate interlocking with each other to move the entire stretch 206 upward and downward.
Of the independent type Z-axial driving mechanisms (FIG. 11) and the non-independent type Z-axial driving mechanisms (FIG. 12), the latter non-independent type driving mechanisms (FIG. 12) are designed so that when the single common motor is driven, the rotations of the motor are communicated to the torsion bar 215 via the worm gear 213 and the pinion 214.
Furthermore, the rotations of the torsion bar 215 are converted to the upward and downward movements of the racks 207A, and as the posts 207 having the racks 207A formed thereon move upward and downward, the stretch 206 also moves upward and downward.
In light of this, the upward and downward movements of the stretch 206 can be said to be controlled by the rotations of the single torsion bar 215, which rotations are in turn controlled by the single common motor.
Due to this, even if the common motor or the like breaks down, no difference occurs in the positions in height at which the right- and left-hand portions of the stretch 206 are located, because both Z-axial driving mechanisms comprising the posts 207, etc. operate simultaneously with each other. Furthermore, if, for example, the common worm gear 213 breaks, both Z-axial driving mechanisms stop simultaneously with each other, while if the torsion bar 215 breaks, both Z-axial driving mechanisms also stop simultaneously with each other, and therefore no difference occurs in the positions in height at which the right- and left-hand portions of the stretch 206 are located.
However, the independent type Z-axial driving mechanisms illustrated in FIG. 11 have structures independent from each other and including their respective Z-axial motors Mz, ball screws, nuts, etc.
Consequently, in the case where one of the Z-axial motors Mz breaks, a difference can occur in the positions in height at which the right- and left-hand portions of the stretch 206 are located, since both Z-axial driving mechanisms operate independently from each other.
As a result, a stress is applied to the entire mechanism including both Z-axial driving mechanisms and the stretch 206, damaging the rotary shafts of the Z-axial motors Mz, the ball screws and nuts incorporated in the posts 207, and the stretch 206, etc. In short, due to a difference in the positions in height at which the right- and left-hand portions of the stretch 206 are located, the back gauge device is damaged mechanically, becoming unusable.
The first object of the present invention is to provide a back gauge device whose workpiece overhang processing range has been enhanced by supporting through utilization of link mechanisms a stretch with abutments attached thereto, while the support condition is stable and a lower space has been ensured.
The second object of the present invention is to provide a back gauge device which prevents applying a stress to the entire mechanism and so avoids mechanical damage, by swinging the stretch in a vertical plane if a difference occurs in the positions in height of the right- and left-hand portions of the stretch.